<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			div{
				width: 100px;
				height: 100px;
				background: red;
			}
		</style>
		<script src="jquery-3.4.1.min.js"></script>
	</head>
	<body>
		<div></div>
		<script>
			$(function(){
				$("div").css("background","green");
			});
		</script>
	</body>
</html>
